This invention relates to radio frequency (RF) communications systems and specifically to multiple RF communications systems collocated on airborne, marine, or ground platforms.
Present airborne, marine, or ground platforms with three or more collocated RF communications systems utilize one or more antennas for each system. Multiple antennas require space in short supply on most platforms, increase drag on aircraft, present unwanted unique platform signatures both visibly and on radar, and interact with each other to distort radiation patterns and degrade communications system performance. All platform users desire to reduce the number of antennas on the platform.
Present systems and methods used to reduce the number of antennas have many deficiencies. One type of system, referred to as a multicoupler, employs agile high power filters for the transmitters and preselectors for the receivers. Also used are signal cancellation techniques. These systems are high cost, large in physical size, have high losses of RF energy, offer poor isolation between ports, have interaction between circuit elements causing producibility and maintenance problems.